JPH02214883A - Method and apparatus for hologram copy - Google Patents

Abstract

PURPOSE: To lessen the undesirable influence of the areas of strong light and dark areas existing in a master hologram by sending a beam for exposure through a light translucent array for optical adjustment modulated according to the information induced from the reconstruction of the master hologram. CONSTITUTION: The beams 26 split by passing a beam splitter 25 are reflected by a concave mirror 29 and arrive at a transparent hologram 30 and a Louvre filter 32 via a liquid crystal matrix 28 from which the beams enter a photosensitive hologram film material 33. The two-dimensional images of the reconstruction hologram via a video-camera 40 are visible on a television screen 45 via a number algorithm 44 when the transparent hologram is reconstructed by using the laser beams before the transparent hologram 30 is exposed on the film material 33. The two-dimensional images of the reconstructed hologram distinctly indicate the areas of the undesirable strong light or the areas of the dark shadows if such areas exist. As a result, such strong light or shade is removed via the number algorithm 44 by operating a keyboard 46.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a method and apparatus for producing copies of holograms. PRIOR ART It is common practice to produce copies of reflective holograms from a reflective master hologram. However, methods have recently been discovered that allow for the production of reflective copies of holograms from transmission master holograms, so whichever method is used, the master hologram is not desirable when reconstructed. Very often it shows areas of no strong light or areas 5 that are too dark. The above-mentioned deficiencies in hologram reproduction cannot be corrected by the burning-in or dotting techniques used in producing positive prints from negatives by conventional photographic enlarging techniques.

[Problem to be solved by the invention]

In view of the above-mentioned drawbacks of the prior art, it would be desirable to develop a method and apparatus for reducing the undesirable effects of intense light areas and dark spots present in a master hologram when producing a duplicate hologram from a master hologram. It was broken. The problem to be solved by the present invention is to provide such a method and apparatus.

[Means to solve the problem]

According to the present invention, as means for solving the above-mentioned problems, in a method for manufacturing a copy hologram from a master hologram, at least some of the members have a light transmission modified according to information derived from the reconstruction of the master hologram. A method of making a copy hologram is provided, the method comprising modifying the light used in the copying process by sending at least one exposure beam through a light conditioning array having a polarity.

The invention also provides an apparatus for implementing the above method, comprising equipment for reconstructing a master hologram, equipment for producing a video signal representative of the reconstructed hologram, and equipment for producing a video signal representative of the reconstructed hologram. a light conditioning array; and a facility for varying the permeability of the members of the light conditioning array based on information derived from the stored signals. An apparatus for manufacturing a multi-chamber hologram is provided.

[Aspects of the invention]

Preferably, the light regulating array is a liquid crystal display (L,
This is an arrangement of liquid crystal pixels known as C, D, ). However, a useful light conditioning arrangement is disclosed in U.S. Pat.
, 375,649 and 4,378,568.

Some of the materials described in the aforementioned US patents are photosensitive materials that can be converted from a non-polar isotropic state to a polar birefringent state by an electric field.

Advantageously, the optical density of each member or pixel in the light conditioning array can be varied to provide a range of light transmission densities.

The light conditioning arrangement is preferably arranged in an X-Y arrangement when the expanded beam is used as the exposure beam. The light conditioning arrangement is preferably an X arrangement when the scanning beam is used as the exposure beam.

The method of the invention can be used to produce a copy of a reflection hologram from a transmission master, or alternatively a copy of a reflection hologram from a reflection master.

In a particularly useful method of producing a copy of a reflection hologram from a transmission master, a laser beam is split to form an objective beam which is passed through a transmission master to be modified;
It penetrates the photosensitive holographic material and interferes with the reflected beam to create holographic interference fringes. In this method, it is preferably the objective beam that is modified through the light conditioning arrangement.

However, the reflected beam can also be modified in this way, or both the objective beam and the reflected beam can be modified.

When a reflection hologram is copied from a reflection master, a photosensitive holographic material is typically placed in substantial contact with the reflection master, and a laser beam is passed through the holographic material to the reflection master, where the holographic image It is modified and reflected back onto the holographic material to produce the objective beam.

In this case, therefore, the laser beam used to expose the holographic material preferably passes through a light conditioning arrangement before entering the holographic material. However, if a very thin light conditioning array is used, it may be sandwiched between the holographic material and the reflective master so that the objective beam is modified by the light conditioning array. can.

One useful method for modifying the optical transparency of a light conditioning array according to information derived from the reconstruction of a master hologram is to reconstruct a master hologram and then holographically reproduce a video signal representing this image. by the use of a video camera positioned along the axis used to view the light, digitize and store this video signal, and then use this stored signal to modify the elements of the light conditioning array.

The stored signal can be fed through a converter to a visual display, such as a television screen, and a two-dimensional master hologram reconstruction is then projected. This displays all of the unwanted bright light and dark shadow areas in the reconstructed image of the master hologram. This image is then corrected by using the keyboard or mouse to change the transformations added to the previous display. This can be done on a point-to-point basis by changing the numerical algorithm regarding the appearance of the reconstructed hologram.

This changes the image on the television screen in real time. When the visible image on the television screen appears satisfactory, the storage signal from the transducer is applied to a light conditioning array where the storage signal selectively modifies its light transmission.

The master hologram is then used for copy printing by using laser light passing through the master.

At least one exposure beam is conditioned by passing through a selectively modified light conditioning array to compress the bright light and dark shadow toner values to create a closer relationship between the master hologram and the photosensitive copying material. Achieve a good agreement. Preferably, the digitized video signal is stored on disk, but may be stored by any convenient digital or analog means, such as a matrix arrangement.

In the method of modifying the light valve arrangement described above, the operator looks at the reconstructed two-dimensional view of the holographic image and decides how it should be modified. However, if the photosensitive properties of the photosensitive material to be used as a copying material are well known, it is also possible to use a so-called "table" that is calibrated using these properties. In this case,
The stored signal is sent to a transducer in the device and the result is read out using a table. The transducer automatically modifies the required amount of transparency of the light valve without any operator manipulation of the parts.

The method of the invention is advantageously used when copying reflection holograms from transmission masters. One of the Applicant's other applications describes a method for making a reflection hologram that involves multiplication of a master transmission hologram into a register containing a sheet of transparent photosensitive holographic material. In this separate application there is a means for cutting zero order light transmitted through the transmission hologram, and there is a light reflecting surface on each side of the assembly including the hologram and holographic material. The method of this co-pending application then generates a fractional beam from a laser source to transmit the entire surface of both the transmission hologram and the holographic material.
Expose I. Kneading is done by directing the beams onto both reflective surfaces, so that one beam is reflected from this reflective surface and, as it passes through the transmission hologram, picks up a thousand φ's of information and transfers it to the transparent photosensitive holographic material. It passes through equipment that cuts the zero-order light and interferes with the other beam, which is reflected from the other reflective surface onto the holographic material. The two split portions of this beam are held in registers. The holographic material is then processed to fix the holographic material.

In one method, a split beam from a laser source scans the entire surface of both the transmission hologram and the holographic material.

In another method, the split beam is directed from a laser source that provides a single total exposure of the photosensitive holographic material. Preferably the laser source is a pulsed laser source. This is because this provides the minimum exposure time. The preferred laser for use in this method is a pulsed ruby laser.

The latter method is illustrated in FIG. 1, which provides a detailed description of the invention.

FIG. 2 is a flow diagram of the equipment components necessary to modify the light conditioning array. The light regulating array in this case is a liquid crystal matrix.

Preferably, the equipment that produces the video signal representing the reconstructed hologram is a video camera.

Preferably, visual facilities are provided for displaying the reconstruction of the two-dimensional master hologram. Most preferably this visual facility is a television screen.

Preferably, the digitized signal is stored on disk.

Preferably, the light adjustment array is a liquid crystal pixel array.

〔Example〕

Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a front view of a copy hologram manufacturing apparatus used to carry out the method of the present invention.

FIG. 2 is a block diagram of the equipment used in the present invention to completely modify the transmittance of members of a light conditioning array.

In Figure 1, a pulsed ruby laser source (21
) is produced as a laser beam (22)' (i=which passes through a beam splitter (25) and is split into two beams (26, 27). The beam (26) passes through a beam expansion facility (34 ) Concave mirror with one plating on the other side (29
) K is reflected by this concave bell (29) and transmitted through the liquid crystal matrix (28) to the hologram (30).
and a loop filter (31) and enters a length (32) of the halogenated@photosensitive holographic film material (33). Loople filter (3
1Hd Cuts zero-order light. Beam (27) is beam expansion equipment (34) fJ' is silver-plated concave surface (29)
> is reflected by this concave surface and enters the same part (32) of said film material (33) where it interferes with the beam (26) for the entire duration of a single pulse emitted by the laser source (21). raise money.

Beam (26) can be considered a response beam or an objective beam. The beam (26) transmits information from the Fi transmission hologram (30) to the film material (33) through the hump. This is because beam (27) can be considered as the ld reference beam. Beam (26) and Beam (27)
are in register when they cause interference in the film material.

Unexposed film is stored in a spool (35);
Exposure I7 film is wound onto spool (36) K. The spool (36) is a drive spool which winds up a predetermined length of exposed film (33) after each pulse from the laser source (21) and simultaneously unloads an equal length of film (33) onto the spool (35). ) and unroll. This ensures that for each pulse exposure a fresh portion of unexposed film (33) is present under the loop filter.

All the film (33) is exposed and the spool (36)
), the exposed film can be processed to fix the holographic stripes.

The apparatus described with reference to FIG.
The optical equipment is particularly useful for making multiple copies of the hologram (30) on a long object, although the hologram (30) can of course be changed at any time during the exposure sequence. It should be understood that the beam (27) coming from the beam splitter (25) is arranged so that it does not directly traverse the path of the photosensitive material (33).

FIG. 2 shows a diagram of the hardware sequence used to modify the liquid crystal matrix (28).

Figure 2 shows the transparent 3f & hologram (30), the video camera (40), the charge coupled device (41) [C, C, I) present in the video camera (40), and the analog/digital converter. (42), disk storage equipment (43),
Numerical algorithms (44), TV screens (4)
5), key board (46), display equipment (
47) and the liquid crystal matrix (28) are shown.

In operation, the transmission hologram (30) is reconstructed using laser light before being exposed onto the film material (33) as described above. A video camera (40) is placed along the axis along which the reproduced hologram is to be viewed;
) captures the reconstructed image of the 2D Shinkin Bank. This is C, C,
T), (41), and the recorded signal is sent to the disk storage # (41) via an A/D converter (42).
43). The stored image signal on the disk (43) is then fed to a television screen (45), and the two-dimensional image of the reconstructed hologram in the transmission hologram (30) is displayed on the television screen (45) via a numerical algorithm (44).
5) Seen above. The two-dimensional image of the reconstructed hologram will highlight any areas of undesirable strong light or dark shadows. Next is the key board (46
) to remove strong light or shadows through a numerical algorithm (44).

Therefore, the laser beams (26... are concave* (2
9) and the photosensitive film material (33) through the transmission hologram (30), the laser beam (
26) is modified by a liquid crystal matrix (28),
When the material (33) is thereby exposed and processed, the reconstructed hologram shows neither undesirable strong light nor dark shadow areas due to the compression of the toner values. Numerical algorithm (44
It should be understood that the function of ) is to transform the stored image information into information with a small dynamic range.

Numerical algorithms can also be connected to lists. This table is calculated for the photosensitivity of the film material (33) and can function to reduce the dynamic range of the stored image, either in conjunction with the operator or automatically without operator assistance. can.

It should be understood that the key board (46) can also be replaced by a so-called mouse to change the appearance of the television screen (45).

[Brief explanation of the drawing]

FIG. 1 is a front view of a copy hologram manufacturing apparatus used to carry out the method of the present invention. FIG. 2 is a block diagram of the equipment used in the present invention to modify the transparency of members of a light conditioning array. 21... Laser light source; 22... Laser beam; 25... Beam splitter; 26,
27... Separation 11 beam; 28... Liquid crystal matrix; 29... Concave mirror; 30... Transmission hologram; 31... Loople filter; 32. 33... Photosensitive holographic material film; 34
... Beam expansion equipment: 35, 36... Spool; 40... Video camera; 41... Charge coupled device (C, C, D,); 42.
...Analog/digital converter; 43...Disk storage equipment; 44...Numeric algorithm 145...
TV screen; 46...key board; 47
...Display equipment.

Claims (1)

[Scope of Claims] 1. A method for producing a duplicate hologram from a master hologram, in which at least some of the members have a light transmittance modified in accordance with information derived from the reconstruction of the master hologram. 1. A method for producing a copying hologram, characterized in that the light used in the copying process is modified by sending at least one exposure beam through the array. 2. Claim 1, wherein the light adjustment array is an array of liquid crystal pixels.
Method described. 3. The method of claim 2, wherein the optical density of each pixel in the array can be varied to provide a range of light transmission densities. 4. The method according to claim 1, wherein an expanded beam is used as the exposure beam and the light adjustment arrangement is an X-Y arrangement. 5. The method according to claim 1, wherein a scanning beam is used as the exposure beam and the light adjustment array is an X array. 6. The optical transparency of the light conditioning array is modified according to information derived from the reconstruction of the master hologram, and the master hologram is reconstructed and a video signal representative of this image is then used to view a copy of the hologram. 2. Obtained by the use of a video camera arranged along the axis of use, the video signal being digitized and stored, and the stored signal then used to modify the elements of the light conditioning array.
Method described. 7. The method of claim 6, wherein the stored signal is provided to a visual display via a conversion device, and the reconstruction of the two-dimensional master hologram is then shown on the display. 8. Apparatus for implementing the method according to claim 1, comprising equipment for reconstructing a master hologram, equipment for producing video signals representing the reconstructed hologram, and digitizing these signals. equipment for storage,
1. An apparatus for producing a copied hologram, comprising a light conditioning array and a facility for changing the transparency of a member of the light conditioning array based on information derived from a stored signal. 9. The apparatus of claim 8, wherein the equipment for producing a video signal representative of the reconstructed hologram is a video camera. 10. The apparatus of claim 8, further comprising visual facilities for showing the reconstruction of the two-dimensional master hologram on a display. 11. The device according to claim 8, wherein the light adjustment array is a liquid crystal pixel array.